The invention relates to an apparatus for separating the gas which evaporates during the transfer of low-boiling liquified gases.
Low-boiling gases such as oxygen, nitrogen and argon are stored and transferred in liquid state for economic reasons. They are used as a cooling medium in many processing methods. The low-boiling liquified gas is then usually in a boiling state. It cannot be avoided that heat from the outside flows into the transfer line. Moreover, heat is also generated in the transferred liquid as a result of friction losses. Since the liquid is in a boiling state, an amount of liquid gas corresponding to the amount of heat evaporates.
A mixture of liquid and gas is, therefore, transferred. This can lead to an undersupply of low-boiling liquified gas at the consumption location. Moreover, the regulating system for the liquid gas supply is overcharged, this sets up vibrations.
In order to eliminate this deficiency, phase separators are used for separating the evaporated gas from the gas which remained liquid. Such phase separators concern, in principle, vessels into which the gas-liquid mixture is fed and where it is separated. The liquid phase and the gas phase are separately withdrawn from these vessels. In order to prevent that too much liquid phase in the form of very fine droplets is discharged with the gas phase, which equals a loss in liquid gas, the gas velocities in the vessel must be kept low. The vessels used as phase separators must, therefore, have a large volumn construction; they are consequently expensive since especially the necessary insulation is very costly. Moreover, additional evaporation losses occur as a result of the large vessel size. A phase separator of this type is shown, for example, in German Pat. No. 26 47 961.
It is known from U.S. Pat. No. 3,206,939 to use a porous hollow body as a phase separator. This has the advantage that the liquid phase emerges in the form of large drops from the porous hollow body and falls down into the catch vessel. These large drops cannot be carried along by the gas phase as a result of which the catch vessel can have a small volume construction. The evaporation losses are, however, still relatively high since a total of three lines, namely the supply line for the gas-liquid mixture and the discharge lines for the gas phase and the liquid phase must be connected to the catch vessel. In order to reduce these evaporation losses, a phase separator consisting of a porous hollow body is arranged in the catch vessel of German Preliminary Application No. 27 43 131 in such a way that all lines are led through a common flange connection into the catch vessel from above. The insulation is, therefore, improved since only one heat bridge is still present.
In spite of the improvements attained with the phase separator of German Preliminary Application No. 27 43 131, the evaporation losses are still considerable. It is, moreover, disadvantageous that the phase separators with their supply and discharge lines must be constructed in different sizes depending on the required throughput of the low-boiling liquified gas.
It became, furthermore, clear that occasionally violent liquid movements occur in the catch vessel wih the phase separator according to German Preliminary Application No. 27 43 131 so that the connected differential pressure switches and possibly directly used float switches do not always produce exact switching procedures.